Ethylene copolymers and terpolymers containing interpolymerized carbon monoxide are well known. Blends of polyvinyl chloride with such ethylene-carbon monoxide copolymers and terpolymers are also well known. For example, in Polymer Blends, edited by D. R. Paul and S. Newman, v. 2, p. 227, Academic Press (New York 1978), it was reported that ethylene-carbon monoxide copolymers containing 15 weight percent or more carbon monoxide were compatible with polyvinyl chloride; however, ethylene copolymers containing less than about 14 weight percent carbon monoxide were reported to be incompatible with polyvinyl chloride. On the other hand, ethylene copolymers containing more than about 15 weight percent carbon monoxide are known to be relatively unstable and present processing problems when employed as plasticizers in polyvinyl chloride. For example, in U.S. Pat. No. 3,156,744, it was reported that when an ethylene copolymer with a carbon monoxide content above about 15 weight percent was employed in a polyvinyl chloride, a reduction in the heat-distortion temperature of the product was engendered. Moreover, the products in this patent were described as opaque plastic alloys, indicating that ethylene-carbon monoxide copolymers with a carbon monoxide content less than about 15 weight percent were not generally compatible with polyvinyl chloride on a molecular scale.
Ethylene-vinyl acetate copolymers have also been used as plasticizers with polyvinyl chloride. Generally, these systems have required the use of an ethylene copolymer with a vinyl acetate content of at least 60 percent by weight. However, because of the relatively high cost of vinyl acetate monomer, ethylene-vinyl acetate copolymers are more expensive than the ethylene-carbon monoxide copolymers. Also, ethylene-vinyl acetate copolymers are a gumstock-type material and are more difficult to blend with polyvinyl chloride than are liquid or powdered plasticizers.
It is also possible to employ as a polyvinyl chloride plasticizer a terpolymer of ethylene, vinyl acetate and carbon monoxide. With such terpolymers, one part interpolymerized carbon monoxide can be substituted for approximately four parts vinyl acetate on a weight basis to obtain a terpolymer similar in compatibility with polyvinyl chloride to ethylene-vinyl acetate copolymers. Such blends are reported, for example, in U.S. Pat. No. 3,780,140.